1. Field of the Invention
The present invention relates to a conveying device which conveys sheets.
2. Description of the Related Art
Among automatic printing plate feeding devices for automatically feeding printing plates to an exposure device, there are those which are equipped with a plurality of cassettes (see, for example, Japanese Patent Application Laid-Open (JP-A) No. 2000-351460). The plural cassettes are respectively disposed parallel to the horizontal direction, and are lined up (in one row) in the vertical direction. Printing plates of different sizes are accommodated or stocked in the respective cassettes.
A pick-up member is provided at such an automatic printing plate feeding device. The pick-up member can pick-up (hold) a printing plate at a predetermined pick-up position. This pick-up position is a position which is set apart, in the horizontal direction, from the uppermost cassette.
A predetermined cassette is moved horizontally from the position at which the plural cassettes are lined up (this position will hereinafter be called the “cassette withdrawn position”). The rear end of the predetermined cassette at the time of this horizontal movement moves away from the cassette withdrawn position. Here, in a case in which the predetermined cassette is other than the uppermost cassette, thereafter, the predetermined cassette reaches the pick-up position by being moved in the vertical direction. In this way, due to the pick-up member picking-up (holding) the printing plate and the pick-up member being moved in this state of holding the printing plate, the printing plate is conveyed. Further, by changing the cassette from which the printing plate is picked-up by the pick-up member (i.e., by changing the predetermined cassette), the size of the printing plate fed to the exposure device is changed.
However, in this automatic printing plate feeding device, the pick-up position at which the printing plate is picked-up by the pick-up member is a single place and is fixed. Therefore, when a cassette other than the uppermost cassette is moved vertically toward the pick-up position, in order for that cassette to not interfere with the other cassettes which are at the cassette withdrawn position, the rear end of the cassette, in the direction of the horizontal movement, must be moved away from the cassette withdrawn position at the time when the cassette is moved horizontally.
In this way, the horizontal distance between the pick-up position and the cassette withdrawn position, i.e., the distance over which the cassette moves horizontally, becomes large, and a problem arises in that the device becomes large.
Moreover, a large mechanism for moving the cassette is needed. Therefore, a problem arises in that the cost of the device increases.
In addition, by making small the region through which the printing plate passes at the time when the pick-up member is moved and the printing plate is conveyed, it is possible to prevent the device from becoming even larger.